Rechargeable battery systems for electric vehicles with purely electric drive and for hybrid vehicles and vehicles with fuel cell drive are the subject of current research. At present, in the said vehicle types, lithium-ion batteries are preferably used, which are distinguished by a high energy density and an only poorly marked, undesired memory effect. The capability of a rechargeable battery to reliably supply with electrical energy various electric consumers installed in motor vehicles depends to a considerable extent on the thermal conditions prevailing in the environment of the battery. This is because the electrochemical processes occurring in the battery both during the provision and also during the receiving of electrical energy—in the sense of recharging—, are dependent to a not insignificant extent on the operating temperature of the battery. Extensive investigations on various lithium-ion-based battery systems have shown, for instance, that below a critical temperature, for instance in the region of approx. 0° C., the electrical energy density provided by the battery decreases greatly compared with higher operating temperatures. Below the critical temperature, in addition damage to the lithium-ion cell can occur during charging.
Accordingly, the creation of thermally well-defined environmental conditions is crucial for a reliable and trouble-free operation of the said batteries—this applies not only for the said lithium-ion-based batteries, but generally for any rechargeable battery systems. This means, with regard to the considerable temperature fluctuations occurring for instance under normal operating conditions in a vehicle, that these must be balanced by suitable temperature control devices which are coupled thermally with the battery, in order to keep the ambient temperature of the battery, and therefore also the temperature of the battery itself, within a predetermined temperature interval. Such a device must be able, on the one hand, to increase the ambient temperature in the immediate environment of the battery, if this assumes a value which lies below the permissible temperature range. On the other hand, the possibility must also exist to lower the ambient temperature, if it exceeds the said temperature interval upwards.
Various devices which are able to be coupled thermally with a battery are known from the prior art, which generally comprise both a heating unit to increase the battery temperature and also a cooling system for lowering the battery temperature.
Thus, in DE 10 2009 90 588 19 A1 a device for heating and cooling a battery is described which has a coolant circuit and at least one electric heating element, which are both arranged in a shared heat transfer component. The electric heating element is connected here in a form- and/or force-fitting manner with the heat transmission component. It is characteristic for the device that it requires a relatively large number of components, which due to the construction are also heated by the heating element during a heating process, which distinctly increases the heating output necessary for the actually aimed for heating of the battery.